Inorganic polyphosphate containing up to several thousand phosphate residues exists in bacteria, fungi and animals as an energy store, a phosphate reservoir and a chelator of metal ions. Exopolyphosphatase (PPx) hydrolyzes polyphosphate in a progressive manner. N-terminal domain of PPx is thought to belong to the sugar kinase/actin/hsp70 super family, but the homology is very low and the C-terminal domain does not show any homology to this family. To unveil the progressive enzyme mechanism and the interesting interactiotns between PPx and long polyphosphate chain, we have tried to determine the structure of PPx. We succeeded in the crystallization of PPx from E.coli and already confirmed that this crystal diffracts to about 2.5 E. But we could not collect enough high resolution data for the structure determination, not only because crystal diffracts very weakly at house machines, but also because it has too large a unit cell (P41212, a = b = 88.5 E, c = 340 E) for many detectors (including some CCD cameras). So we would like to use your beam line which provides the strong x-ray beam and a large detector (Mar).